1. Field of the Invention
The present invention relates to waterbed mattresses and particularly to such mattresses having inserts disposed within the mattress to inhibit wave motion of the water filling the mattress.
2. Description of the Prior Art
The growth of waterbed sales in the marketplace over the past decade is directly attributable to the reduction of wave motion and increased surface firmness of modern water mattresses. To address the wave motion problem, manufacturers have developed wave motion inhibiting provisions of various types, of which the most utilized and effective of these inserts is the so-called "fiber" insert. Fiber inserts typically consist of one or more layers of bonded polyester fiber batt. Multiple layers of fiber are generally held together with ties of twine, strips of vinyl film, or sometimes plastic or aluminum rivets.
Such mattress constructions generally present little or no problem unless the mattress is moved when partially filled with water, i.e., while in the process of draining or filling the mattress. On such occasions, the heavy, wet fiber insert can readily slide into a pile at an end or side of the vinyl mattress shell. If this happens, it is virtually impossible to straighten out the crumpled insert, and the mattress is essentially ruined. Also, if the mattress is subject to a sudden and intense impact, the resulting wave energy can push the fiber insert out of position and into a lump. Again, the end result is usually a dysfunctional mattress.
To combat this problem it has been proposed to somehow anchor these free-floating inserts to the vinyl mattress shell. One approach has been to anchor the inserts to either integral tabs extending from bottom seams of the vinyl mattress shell or to molded, semi-rigid polyvinylchloride (PVC) flanged eyelets sealed to the walls of the vinyl shell.
The problem of anchoring free-floating objects in a water mattress is one of long standing. For example, White, in U.S. Pat. No. 184,487, discloses straps and buckles to hold "sacks" of water together to provide a stable bed surface. Berryman, in U.S. Pat. No. 779,576, uses a similar approach with "tubes" of water. In both of these patents, the applications of straps, ties, etc. are to the exterior of water containers.
Koenigsberg, in U.S. Pat. No. 2,859,455, discloses binding edges of a foam mattress to the perimeter of a foam mattress cover to prevent relative movement between the mattress and cover. Weinstein et al., in U.S. Pat. No. 3,456,270, discloses an air bladder held in position over a water bladder by securing the air bladder edges to upstanding sides of a foam base.
U.S. Pat. Nos. 4,247,962; 4,345,348; and 4,551,873 to Hall disclose various applications of straps sealed to various parts of the vinyl mattress shell for use in anchoring floating baffle inserts in fixed positions within the water mattress. In addition, Johenning, U.S. Pat. No. 5,062,170, discloses tying baffle inserts to molded eyelets affixed to reinforced mattress corner pieces.
All of the foregoing examples have one or more inherent drawbacks. Any type of anchoring element that is sealed to any part of the vinyl mattress shell creates a weak spot which, if stressed, can result in leakage. Vinyl straps and twine ties have a tendency to slip or loosen over time since a slippery film will build up on internal components of a water mattress even with periodic additions of recommended water treatment compounds. Tabs integrally formed with the vinyl sheets are very wasteful of material as significantly larger pieces of vinyl are required to provide for the tabs. In addition, such tabs are typically located very close to sealed seams to minimize material usage, which creates high stress areas due to the fact that the seams at the bottom of the mattress are held rigidly in place by the weight of the water in the mattress. Consequently there is a propensity for ruptures to occur at the seam areas when the tabs are stressed.
In addition, the introduction of molded, thicker and more robust components into the dielectric heat sealing process with 20 mil. calendered PVC mattress sheeting can pose serious problems due to formulation differences and fusing temperature variations attributable to the differences in the materials and thicknesses of materials involved. Semi-rigid, molded eyelets, for example, have very little if any ability to flex or stretch and thus are unable to absorb any significant stress. As a result, the majority of any stress will tend to be transferred to the seams where the eyelets are sealed to the vinyl mattress shell, and leakage can occur. Another problem is the manner in which the tether tie or strap attaches to a fiber insert. In many instances, the tether strap, band, cord, etc. is passed through holes in the fiber layer(s). Fiber batts do not generally possess significant tensile strength near the edges and can readily permit any type of restricting tie to pull or tear out with minimal stress being exerted. While this does not create the potential for leakage, the insert is no longer properly anchored in place, thus creating the insert dislocation problems mentioned above.